Highly sensitive and selective room-temperature NO2 gas sensor based on novel Fe2O3 nanorings/reduced graphene oxide heterojunction nanocomposites

Novel Fe2O3 nanorings/reduced graphene oxide (Fe2O3 NRs/rGO) heterojunction nanocomposites were synthesized by a simple hydrothermal method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier Transform infrared spectrometer and transmission electron microscope (TEM) were used to analysis the microstructure and morphology of Fe2O3 NRs/rGO nanocomposites. Gas sensing results indicated that the optimal NO2 gas sensor based on Fe2O3 NRs/rGO nanocomposites exhibited a room temperature response of 23.8 toward NO2 concentration of 5 ppm, which was 12 times higher than that of α-Fe2O3 nanorings. The HR-TEM results showed that there was a close interface between α-Fe2O3 and rGO, which proved the formation of heterojunction nanocomposite structure. In addition, the sensor based on Fe2O3 NRs/rGO nanocomposites has a short response time of 15 s and excellent NO2 selectivity. The detection limit of NO2 is as low as 1 ppm at room temperature. The enhancement of NO2 sensing performances can be attributed to the improved electronic conductivity, much higher specific surface area, more adsorption sites and the formation of the heterojunction between Fe2O3 nanorings and reduced graphene oxide.